CVE-2008-3803 in IOS
Summary
by MITRE
A "logic error" in Cisco IOS 12.0 through 12.4, when a Multiprotocol Label Switching (MPLS) VPN with extended communities is configured, sometimes causes a corrupted route target (RT) to be used, which allows remote attackers to read traffic from other VPNs in opportunistic circumstances.
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Analysis
by VulDB Data Team • 05/26/2025
The vulnerability described in CVE-2008-3803 represents a critical logic flaw within Cisco IOS software versions 12.0 through 12.4 that specifically impacts Multiprotocol Label Switching Virtual Private Network implementations. This issue manifests when extended communities are configured within MPLS VPN environments, creating a scenario where route target information becomes corrupted during processing. The flaw stems from inadequate validation mechanisms within the IOS routing protocol implementation, particularly affecting how route targets are handled in extended community attributes. Such route targets serve as crucial identifiers that determine which VPN traffic should be processed by specific routing instances, making this vulnerability particularly dangerous in multi-tenant network environments where traffic isolation is paramount.
The technical nature of this vulnerability falls under CWE-254, which encompasses security weaknesses related to inadequate input validation and logic errors in software implementations. The corrupted route target mechanism allows attackers to exploit a race condition or improper state management within the IOS routing table processing. When extended communities are processed, the system fails to properly validate or sanitize the route target information, leading to situations where malicious actors can manipulate routing decisions to access traffic belonging to other VPN instances. This occurs through opportunistic exploitation where attackers observe network behavior and time their actions to coincide with moments when corrupted route target information is processed, effectively bypassing the intended security boundaries between VPN instances.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it fundamentally compromises the security model of MPLS VPN implementations. Network administrators who rely on MPLS VPNs for traffic isolation and security boundaries face a significant risk of unauthorized cross-tenant data access, potentially exposing sensitive corporate information, customer data, or proprietary communications. The opportunistic nature of the attack means that detection is particularly challenging, as the vulnerability may not manifest consistently under normal network conditions, making it difficult to identify when the system is vulnerable. This vulnerability directly violates the principle of least privilege and network segmentation that MPLS VPNs are designed to enforce, creating potential for widespread data exposure across multiple VPN instances within the same network infrastructure.
Mitigation strategies for this vulnerability require immediate implementation of Cisco IOS patches and updates to versions that address the specific logic error in extended community processing. Network administrators should consider implementing additional monitoring mechanisms to detect anomalous routing behavior that might indicate exploitation attempts. The remediation process involves updating IOS software to versions that properly validate route target information during extended community processing, ensuring that corrupted route targets cannot be used to gain unauthorized access to other VPN traffic. Organizations should also review their MPLS VPN configurations to minimize exposure and implement additional security controls such as route filtering, access control lists, and network segmentation measures. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and credential access through network protocol manipulation, requiring comprehensive network security monitoring and incident response procedures to detect and respond to potential exploitation attempts.